The manufacture and mechanical properties of a novel negative Poisson’s ratio 3-component composite

Abstract

Materials with a negative Poisson’s ratio known also as auxetic materials [1] exhibit unusual property of getting thicker when stretched and thinner when compressed. The helical auxetic yarn (HAY) is a recently invented auxetic reinforcing structure for composites [2]. A helical auxetic yarn (HAY) consists of two fibres: a low modulus elastomeric core and a high modulus wrap fibre in a double helix structure. When a tensile load is applied the core of the HAY becomes wider as the wrap straightens out, resulting in a lateral expansion of the core, and therefore a large negative Poisson’ ratio behaviour. The auxetic behaviour of the HAY can be tailored by altering fibre properties, the initial geometry and also the applied strain to comply with specific applications, such as composites [3, 4], blast mitigation, and filtration [5]. This paper introduces a further development to the current HAY by addition of a third component (a sheath). The presence of the sheath is expected to overcome problems such as slippage of the wrap and inconsistency in the initial wrap angle previously encountered during the manufacture of the HAY. The auxetic performance of conventional and novel systems is investigated and Poisson’s ratio data are presented.